[GSBN] Straw Bale House Fire

[Bill Christensen]

At 10:45 AM -0600 4/1/09, Derek Roff wrote:
>I have the beginnings of an idea that I would like to run by 
>everyone for comment.  I'm thinking about situations like the wall 
>fire that David described, or the end of Catherine's description, 
>when all the visible part of the fire is out, and there is time to 
>think and trace down the remaining hotspots inside the walls.  When 
>the plaster is intact, the combustion inside a strawbale wall is 
>borderline- just barely able to sustain itself, if at all.  If we 
>locate a smoldering hot spot, and pull off the plaster in that area, 
>we let in more oxygen. It seems to me that this could risk a 
>flare-up of some sort, perhaps allowing the spread up to the next 
>course or over to the next joint between bales.  In trying to clear 
>out one smoldering hotspot, we might spawn another.  Is there a way 
>to extinguish the hotspot before we remove the plaster?  I think 
>there might be.
>
>What I would like to test, is drilling a small hole in the plaster 
>right below a hotspot.  Then, using a flexible tube to run a stream 
>of CO2, or other inert, non-toxic gas, into the wall for a couple of 
>minutes.  The gas coming out of a compressed gas cylinder becomes 
>very cold, due to expansion.  I think we could decrease the 
>percentage of oxygen present in the wall around the hotspot by a 
>very significant amount.  I suspect that the combination of cold gas 
>and less oxygen could extinguish the hotspot.  Perhaps we should 
>keep the gas flowing while we remove the plaster over the hotspot. 
>This way, instead of oxygen rushing in, we could have CO2 flowing 
>out through the hole that we are creating.  I imagine that this 
>would make opening the hotspots safer, and decrease the chance of 
>fire spreading inside the wall. Removing all the charred straw from 
>the hotspot would be much safer, if all the smoldering was 
>extinguished, and it was already cooled below ignition temperature, 
>before we removed the plaster.
>
>If testing showed that this approach is useful, it would be fairly 
>easy and inexpensive for every SB homeowner to have a cylinder of 
>CO2 on site for this purpose.  Perhaps a standard CO2 fire 
>extinguisher could be made to serve in this process.  What do you 
>think?

This sounds ripe for testing.

All this fire talk, plus our experience doing the ASTM burn tests in 
San Antonio, makes me want to test the different fire-stopping 
characteristics of "standard stack" vs "french dipped" vs bales 
sprayed w/clay slip between courses.

In my spare time, of course.

-- 
Bill Christensen
billc at greenbuilder.com

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